Investigation of a Pollution Plume Observed by the NASA C-23 Sherpa Aircraft during the 2017 OWLETS Campaign

The NASA Ozone Water-Land Environmental Transition Study (OWLETS) sought to examine the land-water gradients of ozone and other constituents that can occur in coastal environments, in particular over the Hampton Roads region and Chesapeake Bay watershed during summer 2017. The understanding of these gradients is critical for the validation of satellites' data products, such as TROPOMI and the upcoming Tropospheric Emissions: Monitoring of Pollution (TEMPO).

As part of OWLETS, measurements of ozone and various trace gases and aerosols were collected by a suite of instrumentation, including, lidars, ozonesondes, Pandoras, AERONET, UAV’s, research vessel, mobile cars, and two NASA aircraft. The C-23 Sherpa aircraft spirals completed on July 19^th and 20^th show the complex variability of ozone over the Chesapeake Bay Bridge Tunnel (CBBT). A particular spiral conducted on July 20^th represents an area of interest and potential pollution plume with a low-level layer of high values of ozone and a variety of trace gases. This plume, also detected by the Langley Mobile Ozone Lidar, was observed to be extremely localized horizontally. To explore its origin, Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model backward trajectories were implemented and calculations of CO/CO₂ ratios were utilized to determine the source's type.

The large variability of ozone and other trace gas analyzed over the CBBT show the importance of OWLETS-like studies for the preparation and validation of missions such as TEMPO.